6PPN

Structure of S. pombe Lsm2-8 with unprocessed U6 snRNA

Summary for 6PPN

• Entry DOI: 10.2210/pdb6ppn/pdb
• Descriptor: Mimic of unprocessed U6 snRNA, U6 snRNA-associated Sm-like protein LSm2, Probable U6 snRNA-associated Sm-like protein LSm3, ... (9 entities in total)
• Functional Keywords: rna, rna binding protein, rna binding protein-rna complex, rna binding protein/rna
• Biological source: Schizosaccharomyces pombe (strain 972 / ATCC 24843) (Fission yeast); More
• Total number of polymer chains: 16
• Total formula weight: 159732.28

Authors

Montemayor, E.J.,Butcher, S.E. (deposition date: 2019-07-08, release date: 2020-06-17, Last modification date: 2023-10-11)

Primary citation

Montemayor, E.J.,Virta, J.M.,Hayes, S.M.,Nomura, Y.,Brow, D.A.,Butcher, S.E.
Molecular basis for the distinct cellular functions of the Lsm1-7 and Lsm2-8 complexes.
Rna, 26:1400-1413, 2020

PubMed Abstract: Eukaryotes possess eight highly conserved Lsm (like Sm) proteins that assemble into circular, heteroheptameric complexes, bind RNA, and direct a diverse range of biological processes. Among the many essential functions of Lsm proteins, the cytoplasmic Lsm1-7 complex initiates mRNA decay, while the nuclear Lsm2-8 complex acts as a chaperone for U6 spliceosomal RNA. It has been unclear how these complexes perform their distinct functions while differing by only one out of seven subunits. Here, we elucidate the molecular basis for Lsm-RNA recognition and present four high-resolution structures of Lsm complexes bound to RNAs. The structures of Lsm2-8 bound to RNA identify the unique 2',3' cyclic phosphate end of U6 as a prime determinant of specificity. In contrast, the Lsm1-7 complex strongly discriminates against cyclic phosphates and tightly binds to oligouridylate tracts with terminal purines. Lsm5 uniquely recognizes purine bases, explaining its divergent sequence relative to other Lsm subunits. Lsm1-7 loads onto RNA from the 3' end and removal of the Lsm1 carboxy-terminal region allows Lsm1-7 to scan along RNA, suggesting a gated mechanism for accessing internal binding sites. These data reveal the molecular basis for RNA binding by Lsm proteins, a fundamental step in the formation of molecular assemblies that are central to eukaryotic mRNA metabolism.

PubMed: 32518066
DOI: 10.1261/rna.075879.120

Experimental method

X-RAY DIFFRACTION (1.91 Å)